Vacuum powered modulators in an adaptive braking system are responsive to an output signal from a control unit to decrease the braking pressure in the brakes of the wheels controlled by the adaptive braking system. A pressure responsive member within the modulator is controlled by vacuum from the engine manifold and the pressure responsive member operates to control the braking pressure communicated to a wheel cylinder.
In view of the limited availability of vacuum from the engine manifold, the modulator is generally large to provide sufficient area contact with the pressure responsive member. Consequently, the modulator crowds the engine compartment which is already crowded with pollution control equipment.
In particular, several modulators include a bypass passage, as illustrated in U.S. Pat. No. 3,790,224, assigned to the same assignee, which adds to the bulky size of the modulator.